Abstract
Field data have proven that, when drilling extended laterals in the Midland Basin, the rate of penetration (ROP) will significantly decline after the rig's surface torque limit is reached. A high-specification drilling system was introduced to combat drilling torque issues which, in turn, produced record-setting performance.
The approach is to identify which factors have the highest impact on drilling torque when using a motor-driven RSS (rotary steerable system) to drill a lateral longer than 10,000 ft. The field dataset analyzed included trajectory design, simulated torque and drag (T&D) versus actual values, hole cleaning effect, mid-lateral cleanup cycle effect, drilling parameters, target formation, and drilling fluids. The outcomes of torque reduction methods are explained in detail, and the final solution is verified with field results. Furthermore, an improvement plan to double the record lateral drilling speed in the Midland basin while staying within rig's capacity, is also discussed.
When drilling laterals longer than 10,000 ft, a motor-driven RSS can produce an ROP of 300 to 400 ft/hr until the mid-lateral point where surface torque reaches 28,000 to 30,000 ft.lbf. This is also close to the torque limit of 5-in. drillpipe. Comparisons between on-bottom and off-bottom torque suggest an oil-based mud (OBM) system yields lower off-bottom torque and friction than a water-based mud (WBM). Simulated and actual T&D data were studied to find that wellbores with tangent profile in the intermediate section, commonly seen in pad well design for anti-collision, contribute to higher bottomhole assembly (BHA) side forces and friction after the wells drill into lateral section. Drilling parameters also plays a significant role in torque induction since they affect interactions between bit and rock. On the formation side, stringers such as limestone reduce torque. Analysis also concluded that mid-lateral cleanup cycles have minimal impact on torque reduction, and OBM is necessary to extend drilling performance in long lateral wells. An RSS powered by a high-specification motor drilled a 7,000-ft lateral in just 21 hours to set a new high mark in the Permian Basin.
